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Red Tide Suspected In Dolphin Deaths

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by Evelina Burnett on

A dolphin rescue display at the Institute for Marine Mammal Studies

Evelina Burnett

Fifty dolphins have died in Mississippi since January. That's more than during all of last year. MPB's Evelina Burnett reports, scientists suspect last year's red tide may be to blame for the unusually high number of deaths.

A dolphin vocalizes during a presentation for school children at the Institute for Marine Mammal Studies in Gulfport. Moby Solangi is director of the institute, which also has a veterinary hospital and is the Mississippi organization permitted to respond to marine mammal strandings. He says the number of dolphin deaths this year is alarming.

"The stranding season has just started, and so far we've had 50 dolphins that have died," Solangi says, "but more concerning is that nine of them are baby dolphins, which were either aborted or died soon after they were born."

The results of tissue and other analysis from the dolphins' necropsies aren't back yet, but Solangi says it looks likely that last year's unusually large harmful algae bloom, or red tide, was a factor.

"Keep in mind, dolphins are the top predator, so the fish that get affected are then eaten by the dolphins which usually are the ones to show their effects much later than the acute affects seen on the fish and other invertebrates," he says.

Right now is also the time of year that baby dolphins are born. Solangi suspects the red tide may have been a factor in those deaths as well.

"In their last trimester of the pregnancy, these animals would have eaten the fish. The toxins have accumlated in the animals, which may have affected the fetuses," he says.

Heidi Lyn is an assistant professor at the University of Southern Mississippi and has worked with dolphins for more than 20 years. She says red tide can cause deaths throughout the marine food chain.

"What we do know about red tides is that they can have toxic effects at multiple layers of the food chain," she says. "So, for example, even if the red tide itself even affected small fish, those fish could be eaten by larger fish, which could affect them. And those fish could be eaten by the dolphins, which could then affect them."

Red tides have been linked to dolphin die-offs in the past. The largest red tide-related die-off was in 1987, when more than 740 bottlenose dolphins stranded along the Atlantic coast.